This is very important:
"Did the 1st century Christians lie that Jesus was going to return in their lifetime. Did Jesus lie about his traveling to the festival of the tabernacles. These were untruths but were not lies. "
Yes, the persons that made people in the first century believe that Jesus would return in their lifetime were lying. Because he didn't arrive. Even if those persons believed that it would happen , it was still very deceptive. The consequenses for those who listened to it vere drastic.
But OK, if you don't like the word liers, you can call them fasle prophets that believed their own false prophecies.
Of course you can make i spin of it like Rutherford did after the big failure with the "millions" campaign and the 1925 failure. He stadedsomething like "it was anyhow a blessing, because it had a stimulating effect on the members preaching activity" (not an exact quote, I know, so in a way I'm probably a lier )